An international conference on the regulation of neurotransmitter release by presynaptic neuronal hetero- and autoreceptors, will be sponsored by the New York Academy of Sciences in December, 1989 in Philadelphia. The proceedings of the conference will be published as an Annal of the Academy in 1990. The presence of receptors on nerve terminals, for a variety of agents, is well established but the reality of functional autoreceptors, responsive to the neurone's own transmitter, is controversial. Although feedback regulation of neurotransmitter release is an immensely attractive hypothesis which introduces terminal regulation into the neurosecretory event, and has far ranging theoretical advantages, its existence and role have been challenged repeatedly over the past ten years. The identification of presynaptic receptors has led to a spate of hypotheses relevant to disease processes and to conditions as diverse as psychosis, mental depression, aging, hypertension and heart failure. The purpose of this conference is to bring together both new and established investigators whose contributions from a range of perspectives will produce a state of the art summary of this newly emerging field, and in an environment which will foster mutual cooperation and the development of new approaches. The symposium will occupy three days. The first day will be devoted to an examination of the different categories of presynaptic receptors including the evidence for their existence, what we know about their operation and possible directions for future work. The second day will deal with transduction mechanisms in the activation of presynaptic receptors, electrophysiology, ions, second messengers and other significant aspects linking receptor activation to alterations in neurosecretion. It is also expected that the second day will have voluntary contributions in the form of poster sessions, and a limited section concerned with some disease processes that may be linked to alterations in presynaptic receptor functions. The third day of the symposium will be devoted to an examination of the question of the existence and physiological relevance of autoreceptors. This conference and its associated publication should help orient both new and established investigators in this rapidly expanding field.